FOR about half its length, “The Mothman Prophecies” plays like an extended episode of “The X-Files” when that show was at its ominous best.

Unfortunately, what looks at first like an affecting, atmospheric thriller veers off into a weepy tale of a husband coming to terms with his wife’s death.

That shift, plus the introduction of tired stock devices like an eccentric expert in the paranormal, would ensure that “The Mothman Prophecies” is ultimately unsatisfying, even if Richard Hatem’s screenplay (from a book by John Keel) did not run out of gas in the last reel.

Washington Post reporter John Klein (Richard Gere, who looks better and better with age) is in a car with his wife, Mary (Debra Messing), at the wheel when she sees something strange in the road and crashes.

They both survive the impact but soon afterwards Mary, who has been suffering from strange hallucinations, dies of a rare cancer.

Two years later, Klein, who hasn’t recovered from his wife’s death, is driving down to Richmond when his car and cell phone mysteriously break down on a lonely country road.

After a violent encounter with an angry, paranoid redneck (Will Patton) Klein is rescued by cute local cop Sgt. Connie Parker (Laura Linney).

He discovers that in 90 minutes, he has somehow driven 400 miles off-course to the creepy town of Point Pleasant, W. Va..

He finds out that similarly inexplicable things have been happening to its inhabitants, including visitations by a tall man with mothlike wings and dreams that are accurately predictive of fatal disasters.

All are somehow related to his late wife’s hallucinations.

Naturally, Klein decides to stay in town to solve the puzzle together with Sgt. Parker and an embittered expert on the paranormal (Alan Bates).

As the plot loses steam, director Mark Pellington (whose paranoid thriller “Arlington Road” was one of the worst movies of 1999) tends to rely on cheap tricks to maintain suspense, although the final catastrophe is very nicely done.

Klein is the right kind of role for Gere: he’s more appealing when he plays a damaged man. Linney, looking like a softer, sexier Helen Hunt, does her best with a role so underwritten it’s almost non-existent. Lucinda Jenney (“Crazy Beautiful”) somehow makes a small role as a madman’s wife remarkably vivid.

David Eigenberg, the monotesticular bartender from “Sex and the City” plays Klein’s assistant at the Washington Post.